Add top-level creation URL for global scope (#37342)

Global scopes have two creation URLs: one for itself and one for the
"top-level" scope. It's not immediately obvious what is considered
top-level here (it is not strictly defined in the specification).

In any case, reports need the creation URL of the scope itself, not the
top-level version. Therefore, propagate this information from all
scopes, where the worker and worklets remain to pass in `None` for their
top-level scope.

Part of #37328

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Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>

components/shared/constellation/from_script_message.rs

@@ -443,7 +443,7 @@ pub struct WorkerGlobalScopeInit {
     /// The origin
     pub origin: ImmutableOrigin,
     /// The creation URL
-    pub creation_url: Option<ServoUrl>,
+    pub creation_url: ServoUrl,
     /// True if secure context
     pub inherited_secure_context: Option<bool>,
 }